Method of lining metallurgical assembly

ABSTRACT

The proposed method relates to metallurgy and foundry engineering. 
     The process of lining a metallurgical assembly, in particular an induction furnace (1) is carried out in the following sequence. First, a bottom (2) is lined using a conventional method, following which a gauge (3) for forming an inner wall of the furnace lining is mounted thereon, and a space (5) provided within the gauge (3) and an induction heater (4) of the furnace (1) is filled with a lining mass (6). The lining mass is filled in layers each having a thickness of 4 to 10 values of said space (5). The layers are compacted by applying periodically repeated blows against the inner surface of the gauge (3). These blows are applied in the direction perpendicular to a plane tangential to said surface of the gauge (3), the interval between the blows being not less than the damping time of free oscillations of the furnace. 
     The above described method may be used when carrying out rammed lining within coreless induction furnaces.

BACKGROUND OF THE INVENTION

1. Technical Field

The invention relates to metallurgy and foundry engineering andparticularly concerns a method of lining a metallurgical assembly.

2. Description of the Prior Art

An important problem encountered by those skilled in the art whendeveloping a technology of lining metallurgical assemblies, e.g.induction furnaces consists in increasing stability of the lining with asimultaneous reduction of expenses required for manufacturing saidlining.

The process of lining a metallurgical assembly is generally carried outas follows (see M. G. Trofimov, Futerovka induktsionnykh pechei, Moscow,"Metallurgia", 1968, pp. 129-132). First, a bottom is lined using aconventional method, following which a gauge for forming an inner wallof the future lining (a crucible) is mounted on said bottom. The spaceprovided between the gauge and a corresponding element of the assembly,forming an outer wall of the lining (in the induction furnace thiselement is an induction heater) is filled with a free-flowing liningmass, e.g. with quartz sand containing binding additives. Following thisthe lining mass is compacted using various methods. The lining thusobtained is then sintered to increase its strength and resistance to theeffect of a melt.

It should be noted that since the lining serves as a separating barrierbetween the melt and the cooled induction heater of the furnace, threezones having different degrees of sintering are present therein, theexistence of these zones being caused by a relatively high temperaturegradient in the direction of the thickness of said lining. The lining ofthe first zone (which is the closest to the melt) is the most sinteredand the strongest one. The lining of the second (intermediate) zone, dueto a lower temperature, is sintered to a lower degree than in the firstzone and is less strong. In the third zone (abutting with the inductionheater of the furnace) of the lining there is almost no sintering sinceindividual grains of the refractory material are practically not boundbetween themselves.

In the course of lining the steps of filling and compacting the liningmass must be carried out in such a manner as to ensure:

(a) the highest degree of compaction in the first zone in order toobtain the minimum porosity and the maximum strength of the lining.These properties are necessary since the lining of this zone is toresist the effect of the melt and melting products;

(b) a lower degree of compaction in the second zone (and a higherporosity);

(c) the lowest degree of compaction in the third zone, i.e. the highestporosity since this zone is to be a buffer one, to provide forcompensation of thermal expansion of the lining, and to lower impacteffect exerted on said lining in the course of charging the furnace.

To increase the resistance of the lining of the assembly, the liningmass is to be uniformly compacted in the direction of the crucibleheight.

Moreover, in the course of lining the initial granular composition ofthe lining mass is to be maintained, i.e. fraction separation thereofmust be eliminated.

In this connection it should be noted that the granular composition ofthe mass and distribution of grains over the volume of the lining massinfluence the ratio between the volumes of closed and open pores and thetotal value of mass porosity, thereby determining numerous properties ofthe lining, and first of all strength and resistance to the effect ofmelt. The granular composition of the mass determines the number ofcontact points between the grains of the refractory material per unit ofvolume. With the optimum granular composition, voids between coarsegrains are filled to the maximum extent with finer grains. The number ofcontact points and consequently density of the lining mass increase,thereby promoting an increase in the lining resistance.

It should be also noted that in the course of lining the local depletionor enrichment of the lining mass with a binder is to be eliminated.

With all the above requirements being met, the lining will possess highoperation reliability.

In order to obtain uniform compaction of the lining mass with thecrucible height, numerous prior art methods of lining providelayer-by-layer filling and compacting said mass. The step of compactingthe layers is usually accomplished by ramming (USSR Inventor'sCertificate No. 500,452).

The disadvantage of such a technology lies in the fact that in thecourse of ramming the lining mass is compacted non-uniformly along thecrucible height, while along the thickness thereof the mass is uniformlycompacted, due to which fact the third (buffer) zone of the lining,which must possess absorption properties, becomes excessively compacted.This results in decreasing the lining durability. Moreover, the step oframming is a laborious and hard-to-mechanize operation, which results ina considerable increase in expenses for making the lining.

Also known in the art is a method of lining wherein, in order to obtainvarious properties in the direction of thickness of a lining, it hasbeen proposed to use different lining masses and to fill them separatelyinto a space provided between the gauge and the induction heater of thefurnace, using a separating jacket (Swiss Patent Specification No.476,272). According to this method, first the bottom of the furnace islined, following which the gauge is mounted, and the jacket is placedbetween the gauge and the induction heater of the furnace, said jacketbeing constructed in the form of a thin-walled shell whose height doesnot exceed the diameter thereof. The jacket is fixed on three verticalhelical rods mounted on the furnace body, said rods allowing the jacketto be either lifted or lowered relative to the bottom. The space betweenthe gauge and the jacket and that provided between the jacket and theinduction heater are filled with corresponding lining masses, the latterbeing subjected to compaction by ramming, shaking or vibratorycompacting. In such a manner the first lining layer (in the direction ofthe crucible height) is formed. Following this, the jacket is lifted toa height corresponding to the thickness of the next layer, and the cycleis repeated. Using several such steps, the lining is made over the wholeheight of the furnace.

An obvious advantage of the above method of lining consists in thepossibility of obtaining the lining having different zones with thecrucible thickness, particularly two zones, and of using cheaperrefractory materials for the outer (more distant from the melt) zonethan those for the inner (more close to the melt) zone of lining.

In the practical realization of this method, however, there arise someserious difficulties. In particular, when compaction of the lining massis accomplished by ramming, as required by an embodiment of the abovetechnology, there arise difficulties similar to those accompanying thestep of ramming in practicing other above described methods of lining.

When, in accordance with another embodiment of the invention, vibratorycompaction is accomplished, the gauge will start vibrating andseparation of the lining mass in accordance with the size of grains intoseparate fractions will occur, the coarse grains accumulating at thegauge. This results in an increase in the lining porosity within thefirst (inner) zone, thereby decreasing the resistance of the liningagainst the effect of the melt.

Moreover, with vibratory compacting the lining mass within the upperportion of the layer being compacted changes to a condition close to thefluidized one, which results in the local depletion or enrichmentthereof with a binder and in a non-uniform compaction in the directionof crucible height. This phenomenon causes lamination of the lining and,as a sequence, penetration of the melt thereinto, which results inreducing service life of said lining.

It should be also noted that in the course of compacting the lining massby means of various vibrators, the organism of a man carrying out liningoperations is subjected to the harmful effect of vibrations.

Compaction of the lining mass, accomplished in accordance with the thirdembodiment of the above technology by shaking results in an increase inthe total porosity of the lining (over the whole volume thereof) and aswell as vibratory compaction, does not ensure uniform compaction of themass in the direction of crucible height.

All the above difficulties inhibit wide practical application of saidtechnology.

SUMMARY OF THE INVENTION

The principal object of the invention is to provide a method of lining ametallurgical assembly, wherein by changing the technology of compactingthe lining mass there is ensured differentiated compaction thereof alongthe thickness and uniform compaction along the height of the crucible,thereby increasing the resistance of the crucible without augmentingexpenses required for manufacturing said crucible.

The object set forth is attained by a method of lining a metallurgicalassembly, comprising steps of lining an assembly bottom, mounting agauge for forming an inner wall of the assembly lining on the linedbottom, layer-by-layer filling a space provided between the gauge and acorresponding element of the assembly forming an outer wall of thelining, with a lining mass while compacting each layer, according to theinvention, the lining mass is filled in layers each having a thicknessof from 4 to 10 values of said space, and compaction of each layer isaccomplished by applying periodically repeating blows against the innersurface of the gauge, the direction of said blows being perpendicular tothe plane tangential to this surface of the gauge, the blows beingapplied with an interval which is not less than the damping time of freeoscillations of the assembly.

Filling the lining mass in layers each having a thickness of from 4 to10 values of said space is the necessary condition to achievehigh-quality compaction thereof.

In the case where thickness of each layer is less than fourfold size ofthe space, the lining turns out to be multilayer which results in adecrease in durability thereof. This fact is caused by fractionseparation of said mass in the upper portion of each layer, and byaccumulation of coarse grains on the surface thereof.

In the case where thickness of each layer is more that tenfold size ofthe space, compaction of the lining mass has a local nature and is notsufficiently complete which fact in some cases may lead to the formationof voids within the mass. Said voids also lower the lining durability.

Application of periodically repeated blows, as hereinbefore described,provides for differentiated compaction of the lining mass in thedirection of crucible thickness. Since the blows are applied against theinner surface of the gauge, the lining mass is compacted to the maximumextent in the first zone being closest to the gauge, to a lesser extentin the intermediate zone, and to the lowest extent in the third (outer)zone.

The time interval of application of the blows must be not less than thedamping time of free oscillations of the metallurgical assembly.Otherwise, the assembly enters the state of forced oscillations. Thelining mass changes to a state being close to fluidized one, which leadsto fraction separation thereof and to local depletion or enrichment withthe binder.

Application points of the blows are preferably distributed over thegauge within the limits of each layer being compacted, in tiers, so thatthe distance between adjacent tiers and the distance between adjacentapplication points of blows in one tier be equal to the magnitude of aspace whereto the lining mass is filled, the lower tier of applicationof blows be disposed at the boundaries between the layer being compactedand the previous one, and the upper tier of application of blows belocated below the upper level of the layer being compacted by the valueof said space, the compaction step is to be accomplished from the lowertier towards the upper one and to be repeated 3 to 5 times for eachlayer being compacted.

Such a distribution of application points of blows makes it possible touniformly compact the mass in the directions of crucible height andperimeter, and inhibits fraction separation of the lining mass along theboundaries between layers being filled. The repeated nature ofcompaction promotes a more uniform distribution of the lining mass overthe whole volume of the lining.

The above number of compaction cycles is optimum. In the case where thenumber of cycles exceeds 5, there may start fraction separation of thelining mass at the gauge, which will lead to an increase in the porosityof the mass within the first zone due to local accumulation of coarsefraction therewithin. This fact results in a decrease in the strengthand resistance of the crucible to the effect of the melt, and in anincrease in labor consumption in the course of making said crucible. Inthe case where the number of cycles is less than 3, there are possiblecases of incomplete compaction of the lining mass within the first zone,which also reduces the strength and resistance of the lining.

To achieve a more uniform compaction of the lining mass in thedirections of crucible height and perimeter with relatively large valuesof said space (more than 150 mm), it is expedient to shift each tierdownwards with each repeated cycle of layer compaction, the value ofthis shift being (δ/N), where δ is the size of the above space, and N isthe number of compaction cycles, and to shift by the same value alongthe tier perimeter the application points of blows.

It is also expedient to reduce the force of blows with each repeatedcycle of layer compaction so that the impulse be decreased by amagnitude of 30 to 40% within the range from 6·10³ to 1.5·10³ N·s.

Such a decrease in the impulse further promotes differentiatedcompaction of the lining mass in the direction of crucible thickness.Absorption properties of the lining are improved, cracking thereof isreduced, and resistance of said lining is upgraded.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more apparent from the followingembodiments thereof with reference to the accompanying drawings, inwhich:

FIG. 1 shows longitudinal sectional view of a coreless induction furnacebeing lined in accordance with the method of the invention;

FIG. 2 shows an axonometric diagram of application of blows against thefurnace gauge in accordance with the proposed method of lining (thearrows show directions of application of blows);

FIG. 3 illustrates, in accordance with the invention, vibrating processwithin the furnace lining in application of blows at an intervalexceeding the damping time of free oscillations of the furnace;

FIG. 4 shows the view similar to that of FIG. 3 in the case where theinterval between the blows is equal to the damping time of freeoscillations of the furnace;

FIG. 5 shows the view similar to that of FIG. 3 in the case when theinterval between the blows is less than the damping time of freeoscillations of the furnace;

FIG. 6 shows the scheme of distribution of application points of blowsover the gauge surface with several cycles of compaction of lining masslayers in accordance with the method of the invention;

FIG. 7 shows schematically the process of compacting the lining mass inaccordance with the invention in the case of location of a monitoringdevice within the furnace lining; and

FIG. 8 shows the diagram of distribution of application points of blowsover the gauge surface for the case specified for FIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

According to the invention, the process of lining a metallurgicalassembly, for example a coreless induction furnace 1 (FIG. 1) is carriedout as follows. First, using a conventional method, a bottom 2 of thefurnace is lined (packed), following which a gauge 3 for forming aninner wall of future lining is mounted on said bottom. An inductionheater 4 is the element forming an outer wall of the lining in the givenfurnace.

Into a space 5 provided between the insulation of the induction heater 4and the gauge 3, lining mass 6 is filled layer-by-layer. Thickness S ofeach layer being filled (for example, layer 6a) is 4 to 10δ, where δ isthe size of the space 5.

Each filled layer of the mass 6 is compacted by applying periodicallyrepeated blows against the inner surface of the gauge 3. The blows areapplied over the whole perimeter of the gauge 3 in the points a₁ . . .a_(i), b₁ . . . b_(i) etc., the direction of each blow having to beperpendicular to a conditional plane "P" which is tangential to theinner surface of the gauge 3 in a corresponding point as shown by arrowsin FIG. 2 (angles α and β between the blow direction, and vertical andhorizontal lines of the plane "P" are 90°).

The time interval between the blows is selected to be not less than thedamping time of free oscillations of the furnace 1 (oscillations of thesystem "gauge-lining-induction heater").

Now consider in more detail the vibrating process of this system, shownin diagrams of FIGS. 3 through 5, wherein time (τ) is plotted along theaxis of abscissae, and amplitude (A) of oscillations, along the Y-axis.

In the case where the blows are applied with an interval t, exceeding orequal to the damping time T of free oscillations of the system, as shownrespectively in FIGS. 3 and 4, then the desired compaction of the liningmass, which is differentiated by zones, is achieved. In so doing, themass is uniformly compacted in the directions of height and perimeter ofthe future crucible.

If the interval t is less than the time T (FIG. 5), the inductionfurnace enters the state of forced (undamped) oscillations, that is whenthe furnace oscillations caused by a previous blow have not yet damped,the oscillations caused by the next blow start. In this case thereoccurs mutual superposition of oscillations, and the resulting vibratingprocess is characterized in the particular case (in the coincidence ofoscillation phases) by a curve which is shown in a dotted line in FIG.5. In this case the lining mass in the upper portion of the layer beingcompacted changes to a state close to the fluidized one, in which statethere occurs its fraction separation and local depletion or enrichmentwith a binder, thereby reducing the lining resistance.

It should be noted that, since in order to increase the liningproductivity the interval t between the blows must be as short aspossible, this interval is to be selected to slightly exceed (by 1 to1.5 s) the time T.

It is advantageous to distribute the application points of blows overthe gauge 3 (FIG. 1) within the limits of each layer 6a being compacted,in tiers a₁, a₂ . . . a_(i), b₁,b₂ . . . b_(i), c₁,c₂ . . . c_(i), d₁,d₂. . . d_(i) so that the distance l₁ between adjacent tiers (e.g. betweenthe tier "c" and the tier "d") and the distance l₂ between adjacentpoints of one tier (e.g. between the points d₆ and d₇) be equal to thevalue δ of the space 5. The lower tier "a" is disposed at the boundarybetween the layer 6a being compacted and the previous layer 6b, and theupper tier "d" is located below the upper level of the layer 6a by avalue l₃ which is equal to the value δ of the space 5. Compaction iscarried out from the bottom upwards from the tier "a" to the tier "d",and is repeated 3 to 5 times for each layer being compacted.

Such an application of blows promotes the uniform distribution of thelining mass 6 over the whole volume of the space 5 between the gauge 3and the induction heater 4, and uniform compaction thereof both overperimeter and height of the furnace crucible being formed, and inhibitsfraction separation of the mass 6 along the boundaries between thelayers.

In the case where the value δ of the space 5 in a metallurgical assemblyreaches a comparatively large value (more than 150 mm), then in order toincrease the compaction uniformity of the lining mass in the directionof crucible height it is recommended to apply blows as shown in FIG. 6.In this case with each repeated compaction cycle, each tier is shifteddownwards by a value "K" being of (δ/N), where δ is the size of thespace 5, and N is a selected number of compaction cycles, theapplication points of blows being shifted over the tier perimeter by thesame value "K". Thus, in the first compaction, blows are applied againstthe gauge 3 in the points a₁ . . . a_(i), b₁ . . . b_(i), c₁ . . .c_(i), d₁ . . . d_(i) (which are designated by light circles for theillustrative purpose); in the second compaction the blows are applied inthe points a₁ ' . . . a_(i) ',b.sub. 1 ' . . . b_(i) ', c₁ ' . . . c_(i)', d₁ ' . . . d_(i) ' (semi-blackened circles); and in the thirdcompaction in the points a₁ " . . . a_(i) ", b₁ " . . . b_(i) ", c₁ " .. . c_(i) ", d₁ " . . . d_(i) " (dark circles) etc.

In practicing the inventive method, the best results are achieved in thecase where with each repeated compaction cycle the force of blows is soreduced that the impulse be decreased by the value of from 30 to 40%within the limits of 6·10³ to 1.5·10³ N·s. This fact further promotesdifferentiated compaction of the lining mass 6 (FIG. 1) within the space5, thereby improving damping properties of the assembly lining andupgrading the resistance thereof.

In the event that within the furnace lining is mounted a monitoringdevice, e.g. a light conducting block 7 (FIG. 7) for transmission of thethermal radiation from the melt to a pyrometer (not shown), said blockbeing disposed horizontally in such a manner that one end thereofcontacts the gauge 3, while the other end extends outwards through anopening provided in the induction heater 4 of the furnace 1, the processof compacting the lining mass 6 is carried out as follows.

The layer of the mass 6 wherein the light conducting block 7 isdisposed, is compacted in several cycles by means of blows against thegauge 3 (see also FIG. 8) in a manner described above (the applicationpoints of blows of the last cycle are designated by light circles a₆ . .. a₁₀, b₆ . . . b₁₀ etc.) except for a zone being directly adjacent thelight conducting block 7. This zone of the gauge 3 is defined by acircle being concentric to an end face 7a of the light conducting block7, and is designated in FIG. 8 by semi-blackened and dark circles f₁, f₁' etc. The radius R of said circle is equal to δ+(m/2), where δ is thesize of the space 5 (FIG. 1), m is the maximum transverse dimension ofthe monitoring device (in the given case being the diameter of the lightconducting block 7).

Said zone starts to be compacted after the last cycle of compaction ofthe main portion of a layer of the mass 6 is over, said compaction beingcarried out by blows whose direction is shown by the arrows in FIG. 7,against the points f₁, f₂ . . . f₆ of the circle, shown in FIG. 8.

Compaction of said zone may be also carried out in several cycles, thestarting force of blows being selected the same as in the last cycle ofcompaction of the main portion of the layer of mass 6, i.e. having theminimum magnitude, following which said force is reduced during eachcycle by 30 to 40%. In this case the application points of blows areshifted along the circle with each cycle by the same value "K" beingequal to (δ/N), which has been above described in detail. FIG. 8illustrates a particlar case where compaction of said zone is carriedout in two cycles, the points f₁ . . . f₆ corresponding to the firstcycle, (semi-blackened circles), while the points f₁ ' . . . f₆ ' (darkcircles) correspond to the second cycle.

The process of compacting said zone is carried out till the lightconducting block 7 (FIG. 7) stops turning about the axis thereof withinthe lining mass 6. Such a technology of compacting the lining mass 6 inthe zone of location of the light conducting block 7 cannot cause thedamage of the latter and at the same time ensures reliable fixation andoperation thereof within the lining of the furnace 1, and alsoeliminates the possibility of break-through of the melt through thecrucible in this zone.

It should be noted that the above described method of lining ametallurgical assembly can be practiced by means of relatively simpledevices and mechanisms, due to which fact the process of lining may beeasily mechanized. Moreover, the proposed technology of compacting thelining mass 6 eliminates the effect of harmful vibrations on the humanorganism since any frequency of application of blows against the gauge 3can be selected, the single condition consisting in that the intervalbetween these blows be not less than the damping time of freeoscillations of the assembly.

The invention is further explained in terms of specific examples oflining a metallurgical assembly, in particular an induction furnace,according to the inventive method.

EXAMPLE 1

The process of lining a coreless induction furnace having a capacity of6 t, was carried out as follows.

Next to lining a bottom and mounting a gauge, said steps being carriedout in a conventional manner, a lining mass consisting from quartziteand required binding additives was filled layer-by-layer in a spaceprovided between the gauge and an insulation of an induction heater. Thesize of the space (δ) was 150 mm, and the thickness of each layer of themass (S) was 600 mm.

In accordance with the inventive method, each filled layer of the masswas compacted by applying blows against the inner surface of the gaugein the direction perpendicular to the plane P (FIG. 2). The blows wereapplied with an interval (t) being of 2 s. The time (T) of damping freeoscillations of the furnace was 1 s. The application points of blowsagainst the gauge were distributed in tiers within the limits of eachlayer being compacted. The distance between adjacent tiers and thedistance between adjacent application points of blows of one tier wereof 150 mm. The lower tier was located at the boundary between the layerbeing compacted and the previous one, and the upper tier was disposedbelow the upper level of the layer by a distance of 150 mm.

Each layer was compacted 3 times (N), the force of blows being reducedwith each subsequent time in such a way that the impulse (I) wasdecreased by the value of 40% (Δ) and was correspondingly: I₁ =6·10³N·s; I₂ =3.6 10³ N·s; I₃ =2.2·10³ N·s.

The lining thus compacted and then sintered operated satisfactorilyduring the reference period (1,000 h). Subsequent analysis of the liningdemonstrated that the granular composition thereof was uniform both inthickness and height directions of the crucible, the lining having threeclearly defined concentric zones: the first zone (being in contact withthe melt) was the most sintered and saturated with melting products (themost metallized); the second zone (intermediate) was less sintered, lessstrong and more porous. In the third zone the grains of the refractorymaterial were not bound therebetween, the greatest, and the density wasthe lowest, thereby rendering this zone damping properties. Due to thisfact the break-through of the melt from the crucible outside the furnacewas eliminated.

EXAMPLE 2

The process of lining the furnace was carried out mainly as described inExample 1.

Some process parameters were changed to the following values:

S--900 mm

t--1.5 s

N--4

Δ--35%

I₁ --6·10³ N·s

I₂ --3.9·10³ N·s

I₃ --2.5·10³ N·s

I₄ --1.6·10³ N·s

The lining thus obtained operated satisfactorily during the wholereference period. In addition, the depth of the lining metallization wasless than in Example 1, thereby increasing resistance thereof to theeffect of the melt.

EXAMPLE 3

The process of lining the furnace was carried out mainly as described inExample 1.

Some process parameters were changed to the following values:

S--1,200 mm

N--5

Δ--30%

I₁ --6.0·10³ N·s

I₂ --4.2·10³ N·s

I₃ ·2.9·10³ N·s

I₄ --2·10³ N·s

I₅ --1.4·10³ N·s

The lining thus obtained operated satisfactorily during the wholereference period. In addition, the depth of the lining metallization wasless than in Example 2.

EXAMPLE 4

The process of lining the furnace was carried out mainly as described inExample 1.

Some process parameters were changed to the following values:

S--1,500 mm

N--3

Δ--40%

I₁ --6.0·10³ N·s

I₂ --3.6·10³ N·s

I₃ --2.2·10³ N·s

The lining thus obtained operated satisfactorily during the wholereference period.

EXAMPLE 5

The process of a coreless induction furnace having a capacity of 10 twas carried out mainly as described in Example 1. The space between theinsulation of the induction heater and the gauge was of 170 mm, and thedamping time of free oscillations was of 1.2 s. As against Example 1,some process parameters were changed to the following values:

S--1,360 mm

N--5

Δ--40%

I₁ --6.0·10³ N·s

I₂ --3.6·10³ N·s

I₃ --2.2·10³ N·s

I₄ --1.9·10³ N·s

I₅ --1.1·10³ N·s

The lining thus obtained operated satisfactorily during the wholereference period.

EXAMPLE 6

The process of lining a furnace was carried out mainly as described inExample 1. Some process parameters were changed to the following values:

S--1,200 mm

N--10

Δ--10%

I₁ --6.0·10³ N·s

I₂ --5.4·10³ N·s

I₃ --4.9·10³ N·s

I₄ --4.4·10³ N·s

I₅ --4.0·10³ N·s

I₆ --3.6·10³ N·s

I₇ --3.2·10³ N·s

I₈ --2.9·10³ N·s

I₉ --2.6·10³ N·s

I₁₀ --2.3·10³ N·s

The lining thus obtained operated satisfactorily. However due to thefact that the number of compaction cycles exceeded the recommended one,damping properties of said lining were lower than those in Example 1.This resulted in crack formation in some places of the lining, throughwhich cracks the melt penetrated thereinto. In some regions thereoccurred accumulation of coarse fraction of the lining mass at the gaugesurface and along the boundaries between filled layers, therebyresulting in an increase in the porosity and metallization depth of thelining in these places.

EXAMPLE 7

The process of lining a furnace was carried out mainly as described inExample 1. In the course of repeated compaction the blows were soapplied that the impulse value decreased by 50% (Δ), the magnitude ofthe impulse decrease was below the recommended value. Other processparameters were changed to the following values:

S--900 mm

N--3

I₁ --3.0·10³ N·s

I₂ --1.5·10³ N·s

I₃ --0.7·10³ N·s

The lining thus obtained operated satisfactorily, though the porosity inthe first zone thereof was higher than that in Example 1, therebyresulting in an increase in the metallization depth of the lining.

EXAMPLE 8

The process of lining a furnace was carried out mainly as described inExample 1. Blows were applied in five cycles in such a manner that theimpulse in the first two compaction cycles exceeded the recommendedvalue and was:

I₁ --10·10³ N·s

I₂ --7·10³ N·s

Other process parameters were changed to the following values:

S--1,200 mm

Δ--30%

I₃ --5·10³ N·s

I₄ --3.5·10³ N·s

I₅ --2.5·10³ N·s

The lining thus obtained operated satisfactorily, though its granularcomposition was non-uniform in some places in the direction of thecrucible thickness, and damping properties were lower than those inExample 1, thereby resulting in an increase in the metallization depthof the lining.

EXAMPLE 9

The process of lining a furnace was carried out mainly as described inExample 1. The value (δ) of the space provided between the gauge and theinsulation of the induction heater was 180 mm. The number (N) ofcompaction cycles of the lining mass and the impulse values in eachcycle were the same as in the above Example. Each tier of blowapplication was shifted downwards with each repeated cycle along thegauge by a distance of 60 mm (δ/N), the application points of blowsbeing shifted along the tier perimeter by the same distance (FIG. 6).

In spite of a significant size of the above space, the lining thusobtained operated satisfactorily during the whole reference period.

EXAMPLE 10

The process of lining a furnace was carried out mainly as described inExample 1. The value (δ) of the space provided between the gauge and theinsulation of the induction heater was 300 mm. The number (N) ofcompaction cycles of the lining mass and the impulse values in eachcycle were the same as those in Example 3. Each tier of blow applicationwas shifted downwards with each repeated compaction cycle along thegauge by a distance of 60 mm (δ/N), the application points of blowsbeing shifted along the tier perimeter by the same distance (FIG. 6).

In spite of a significant size of the above space, the lining thusobtained operated satisfactorily during the whole reference period.

EXAMPLE 11 (NEGATIVE)

The process of lining a furnace was carried out mainly as described inExample 1. The thickness of each layer of the lining mass being filledwas less than the recommended value and was of 150 mm. Other processparameters were changed to the following values:

t--1 s

N--3

Δ--40%

I₁ --6.0·10³ N·s

I₂ --3.2·10³ N·s

I₃ --2.2·10³ N·s

The granular compositions of the lining thus obtained was nonuniform inthe direction of the crucible height, due to which fact along theboundaries of the filled layers there was observed a local metallizationof the lining to a considerable depth, thereby causing the danger ofbreak-through of the melt from the crucible and beyond the furnace.

EXAMPLE 12 (NEGATIVE)

The process of lining a furnace was carried out mainly as described inExample 1. The thickness of the filled layer was more than thatrecommended, of 2,000 mm. Other process parameters were changed to thefollowing values:

N--4

Δ--35%

I₁ --6.0·10³ N·s

I₂ --3.9·10³ N·s

I₃ --2.5·10³ N·s

I₄ --1.6·10³ N·s

The lining thus obtained had considerable local unsoundness, due towhich fact the melt penetrated thereinto to a relatively large depth (tothe third, buffer zone). This caused the danger of break-through of themelt from the crucible and beyond the furnace.

EXAMPLE 13 (NEGATIVE)

The process of lining a furnace was carried out mainly as described inExample 1. The blows were applied at an interval of 0.3 s. Other processparameters were changed to the following values:

S--900 mm

I--6.0·10 N·s

Due to the fact that in the course of lining the interval between theblows was shorter than the recommended one, the "gauge-lining-inductionheater" system was in the state of forced oscillations, and the liningmass passed to a state close to the fluidized one. This caused depletionin one places, and enrichment in others of the lining mass with abinding agent, and fraction separation of said mass. The melt penetratedinto the lining to a considerable depth, thereby causing the danger ofthe melt break-through from the crucible and beyond the furnace.

While particular embodiments of the inventive method of lining have beenshown and described, various modifications thereof will be apparent tothose skilled in the art and therefore it is not intended that theinvention be limited to the disclosed embodiments or to the detailsthereof and the departures may be made therefrom within the spirit andscope of the invention as defined in the appended claims.

INDUSTRIAL APPLICABILITY

The invention may prove most advantageous when carrying out rammedlining within coreless induction furnaces. In addition, it may beapplied in lining metallurgical and foundry assemblies of other types.

What is claimed is:
 1. A method of lining a metallurgical assembly,comprising steps of lining an assembly bottom, mounting a gauge forforming an inner wall of the assembly lining on the lined bottom,layer-by-layer filling a space provided between the gauge and acorresponding element of the assembly forming an outer wall of thelining, with a lining mass while compacting each layer, wherein thelining mass (6) is filled in layers each having a thickness of from 4 to10 values of said space (5), and compaction of each layer isaccomplished by applying periodically repeating blows against the innersurface of the gauge (3), the direction of said blows beingperpendicular to the plane tangential to this surface of the gauge (3),the blows being applied with an interval which is not less than thedamping time of free oscillations of the assembly (1).
 2. A method asset forth in claim 1, wherein application points of blows aredistributed over the gauge (3) within each layer being compacted and intiers (a₁ . . . a_(i), b₁ . . . b_(i), c₁ . . . c_(i), d₁ . . . d_(i))so that the distance between adjacent tiers and the distance betweenadjacent application points of blows of one tier are equal to the sizeof the space (5) whereto the lining mass (6) is filled, the lower tier(a₁ . . . a_(i)) of application of blows being located along theboundary between the layer being compacted (6a) and the previous one(6b), and the upper tier (d₁ . . . d_(i)) of application of blows isdisposed below the upper level of the layer being compacted (6a) by thesize of said space (5), the step of compaction being carried out fromthe lower tier (a₁ . . . a_(i)) to the upper one (d₁ . . . d_(i)), andrepeated 3 to 5 times for each layer being compacted.
 3. A method as setforth in claim 2, wherein with each repeated cycle of compaction of thelayer (6a), each tier (a₁ . . . a_(i), b₁ . . . b_(i), c₁ . . . c_(i),d₁ . . . d_(i)) is shifted downwards to a value of (δ/N), where δ is thesize of said space (5), and N is the number of compaction cycles,application points of blows being shifted by the same value along thetier perimeter.
 4. A method as set forth in claim 2, wherein with eachrepeated cycle of compaction of the layer (6a) the force of blows isreduced so that the impulse be decreased by 30 to 40% within the rangeof 6·10³ to 1.5·10³ N·s.
 5. A method as set forth in claim 3, whereinwith each repeated cycle of compaction of the layer (6a) the force ofblows is reduced so that the impulse be decreased by 30 to 40% withinthe range of 6·10 to 1.5·10³ N·s.